Buried contact interconnected thin film and bulk photovoltaic cells

ABSTRACT

A semiconductor substrate material having a photovoltaic cell, a semiconductor substrate material having an integrated array of at least two photovoltaic cells in electrical series with one another, systems for the production of electricity and method for the production of electricity are disclosed. In the semiconductor substrate material (301) having a photovoltaic cell (303, 304), the photovoltaic cell comprises at least one first type groove (305, 306, 307) having walls doped with a first type dopant (308), the first type groove having a first conducting material in conducting electrical contact with the first type doped walls and at least one second type groove (310, 311, 312) having walls doped with a second type dopant, the second type groove having a second conducting material in conducting electrical contact with the second type doped walls. The first and second type grooves are electrically lined with each other by at least one doped region of linking substrate material (314, 316) selected from the group consisting of a first type region of linking substrate material and a second type doped region of linking substrate material, thereby forming a photovoltaic junction where the doped linking substrate material forms a junction with doped substrate material of different polarity. The first type dopant is of different polarity from the second type dopant.

TECHNICAL FIELD

This invention relates to a semiconductor substrate material having aphotovoltaic cell, a semiconductor substrate material having anintegrated array of at least two photovoltaic cells in electrical serieswith one another, systems for the production of electricity, and methodsfor the production of electricity.

BACKGROUND ART

One proposed method for reducing the cost of photovoltaic energyconversion is to deposit the photovoltaic solar cells in the form of athin sheet onto a supporting substrate such as glass. Such sheets can bedeposited more or less continuously onto a moving substrate or by othermethods. Techniques are then required to define individual cells withinthis deposited sheet and to provide for their electricalinterconnection.

It would be advantageous at least from a manufacturing viewpoint if theindividual cells in the substrate cell were such that they could befabricated in a wide range of substrate materials, depositionconditions, and cell designs. It would also be advantageous if theinherent features of cells permitted relatively large area individualcells and large scale integrated arrays of cells to be fabricated.

OBJECTS OF INVENTION

It is an object of this invention to provide a semiconductor substratematerial having a photovoltaic cell, and, a semiconductor substratematerial having an integrated array of at least two photovoltaic cellsin electrical series with one another.

Other objects are to provide systems for the production of electricityand methods for the production of electricity.

DISCLOSURE OF INVENTION

According to a first embodiment of this invention there is provided asemiconductor substrate material having a photovoltaic cells,

said photovoltaic cell comprising:

at least one first type groove having walls doped with a firstconductivity dopant, the first type groove having a first conductingmaterial in conducting electrical contact with the first type dopedwalls;

at least one second type groove having walls doped with a secondconductivity type dopant, the second type groove having a secondconducting material in conducting electrical contact with the secondtype doped walls;

the first and second type grooves being electrically linked with eachother by at least one doped region of linking substrate materialselected from the group consisting of a first conductivity type dopedregion of linking substrate material and a second conductivity typedoped region of linking substrate material, thereby forming aphotovoltaic junction where the doped linking substrate material forms ajunction with doped substrate material of different type conductivity;and

the first conductivity type dopant being of opposite type from thesecond conductivity type dopant.

According to a second embodiment of this invention there is provided asemiconductor substrate material having an integrated array of nphotovoltaic cells in electrical series with one another,

each photovoltaic cell being as defined in the first embodiment;

said n photovoltaic cells in the substrate material being in electricalseries with one another, n being greater than or equal to 2, whereby anm_(j) -1)th cell is electrically coupled to an m_(j) th cell via aconfiguration selected from the group consisting of:

(i) the first conducting material of the first conductivity type grooveof an (m_(j) -1)th cell is electrically coupled via interconnectingconducting material with the second conducting material of the secondconductivity type groove of an m_(j) th cell; and

(ii) the second conducting material of the second conductivity typegroove of the (m_(j) -1)th cell is electrically coupled viainterconnecting conducting material with the first conducting materialof the first conductivity type groove of the m_(j) th cell;

where j is greater than or equal to 2 and less than or equal to n andm_(j) is equal to j; and

wherein first type doped walls of the first conductivity type groove ofeach photovoltaic cell in the substrate material are substantiallyelectrically insulated from first type doped walls of first conductivitytype grooves of other photovoltaic cells in the substrate material andsecond type doped walls of the second conductivity type groove of eachphotovoltaic cell in the substrate material are substantiallyelectrically insulated from second type doped walls of secondconductivity type grooves of other photovoltaic cells in the substratematerial.

According to a third embodiment of this invention there is provided asystem for the production of electricity, the system comprising:

(a) a semiconductor substrate material having a photovoltaic cell, inaccordance with the first embodiment; and

(b) an electrical circuit in electrical communication with the firstconducting material of the first conductivity type groove of the cell,and the second conducting material of the second conductivity typegroove of the cell.

According to a fourth embodiment of this invention there is provided asystem for the production of electricity, the system comprising:

(a) a semiconductor substrate material having an integrated array of nphotovoltaic cells in electrical series with one another, in accordancewith the second embodiment; and

(b) an electrical circuit in electrical communication with conductingmaterial selected from the group consisting of:

(1) the first conducting material of the first conductivity type grooveof the first cell, with the proviso that, except via the electricalcircuit, the first conducting material is not electrically coupled viainterconnecting conducting material with the second conducting materialof the second conductivity type groove of another cell in the electricalseries, and

the second conducting material of the second conductivity type groove ofthe nth cell, with the proviso that, except via the electrical circuit,the second conducting material is not electrically coupled viainterconnecting conducting material with the first conducting materialof the first conductivity type groove of another cell in the electricalseries; and

(2) the second conducting material of the second conductivity typegroove of the first cell, with the proviso that, except via theelectrical circuit, the second conducting material is not electricallycoupled via interconnecting conducting material with the firstconducting material of the first conductivity type groove of anothercell in the electrical series, and

the first conducting material of the first conductivity type groove ofthe nth cell, with the proviso that, except via the electrical circuit,the first conducting material is not electrically coupled viainterconnecting conducting material with the second conducting materialof the second conductivity type groove of another cell in the electricalseries.

According to a fifth embodiment of this invention there is provided amethod for the production of electricity, the method comprising:

illuminating the junction of the system of third embodiment with lightcapable of generating photocurrents at the junction whereby currentflows through the cell thereby loading the electrical circuit.

According to a sixth embodiment of this invention there is provided amethod for the production of electricity, the method comprising:

illuminating the junctions of the system of fourth embodiment with lightcapable of generating photocurrents at the junctions whereby currentflows through the n cells thereby loading the electrical circuit.

The number n of cells may be very large, eg 100 and more. Typically anarray contains 2 to 5,000 cells, more typically 2 to 500 cells or 2 to100 cells, and even more typically 6 to 50 cells or 6 to 25 cells.

Shunting diodes may be incorporated in the array in accordance with U.S.Pat. No. 4,323,719, the contents of which are incorporated herein byreference.

Techniques for the formation of grooves in solar cells are described inU.S. Pat. Nos. 4,748,130 and 4,726,850, the contents of which areincorporated herein by reference.

Techniques for the solution growth of silicon films are described inAustralian Patent Application No. 31215/89, the contents of which areincorporated herein by reference.

The first and second conductivity type dopants may be n-type, p-type, n⁺-type, or p⁺ -type dopants with the proviso that the first conductivitytype dopant is of opposite type to the second conductivity type dopant.

The first and second conducting materials can be the same or differentand can be a metal (eg aluminum), conducting polymer, metal alloy, dopedsemiconductors or other appropriate conducting material. Generally theconducting material is chosen so that it forms a good electrical contact(preferably an ohmic contact) with the walls of the groove(s) with whichit is in contact.

The photovoltaic cells of the invention are particularly useful inconverting solar light, light from light sources such as tungsten lamps,fluorescent tubes, photodiodes, or lasers into electricity.

The interconnecting conducting material may be the same or differentfrom the first and second conducting materials and can be a metal,conducting polymer, metal alloy, doped semiconductor, or otherappropriate conducting material.

The semiconductor substrate material can be thin films, single crystal,or polycrystalline material. It may be continuous or discontinuous. Thinfilms may be supported on a substrate or superstrate such as glass,quartz, perspex, or other suitable superstrate. When the superstrate istransparent to the illuminating light the array can be illuminatedthrough the superstrate. The semiconductor substrate material may beused with appropriate antireflection coatings and fabricated usingappropriate antireflection geometries.

Typically, the photovoltaic cell is a solar cell. Semiconductorsubstrate materials such as silicon, germanium, CdTe, CuInSe₂, GaAs,AlGaAs, GaP, GaAsP, SiC, InP, and other photovoltaically activesemiconductors are particularly suitable for p-n photovoltaic cells andparticularly for p-n photovoltaic solar cells.

Significant advantages of the present invention are that is provides anew way of both isolating individual photovoltaic cells in a substrateand of providing electrical interconnection. The technique is applicableto a wider range of materials deposition conditions and cell designs andallows individual cells to be much longer (5-25 cm) than possible withpresently established photovoltaic arrays. The photovoltaic arrays canbe of unlimited length since the highly conductive conducting materialin the grooves can carry current long distances with minimum resistancelosses. The substrate or superstrate provides a high lateral resistancebetween the lower regions of the grooves of different cells to ensureeffective isolation of like polarity grooves between individual cells.The technique allows for the use of grooves with tin film photovoltaiclayers and provision of metal contacts to the layers via conductingmaterial such as metal in the grooves. A cell can have grooves ofopposite polarity interdigitated with each other to minimise photoactivespace lost as well as providing a parallel current path tointerconnecting grooves which interconnect the photovoltaic cells inseries and at the same time providing for low resistance losses.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts a thin film semiconductor substrate material on a glasssuperstrate having an integrated array of only two photovoltaic cells inelectrical series with one another in accordance with one embodiment ofthe invention;

FIG. 2 depicts alternating n-type and p-type thin film silicon layers ona supporting glass superstrate and having an oxide or other insulatingmasking layer on the top n-type silicon layer representing a structureinto which an integrated array of two photovoltaic cells may be formedin accordance with another embodiment of the invention;

FIG. 3 depicts a cross sectional view of thin film semiconductorsubstrate material on a glass superstrate of FIG. 2 having an integratedarray of two photovoltaic cells in electrical series with one another;

FIG. 4 depicts a cross sectional view of another type of thin filmsemiconductor substrate material on a glass superstrate of FIG. 2 havingan integrated array of two photovoltaic cells in electrical series withone another;

FIG. 5 depicts p⁺ -type layer, i layer, and n⁺ -type thin film siliconlayers on a supporting glass superstrate and having an oxide or otherinsulating masking layer on top of the p⁺ -type silicon layer;

FIG. 6 depicts a perspective cross sectional view of thin filmsemiconductor substrate material on a glass superstrate of FIG. 5 havingan integrated array of photovoltaic cells in electrical series with oneanother;

FIG. 7 depicts a plan view of a thin film semiconductor substratematerial on a glass superstrate having an integrated array of threephotovoltaic cells in electrical series with one another in accordancewith a further embodiment of the invention;

FIG. 8 depicts a plan view of a thin film semiconductor substratematerial on a glass superstrate having an integrated array of fivephotovoltaic cells in electrical series with one another in accordancewith another embodiment of the invention;

FIG. 9 depicts a plan view of a thin film semiconductor substratematerial on a glass superstrate having an integrated array of fourphotovoltaic cells in electrical series with one another in accordancewith another embodiment of the invention;

FIG. 10 depicts a plan view of a thin film semiconductor substratematerial on a glass superstrate having an integrated array of fourphotovoltaic cells in electrical series with one another in accordancewith another embodiment of the invention;

FIG. 11 depicts a cross sectional view of thin film semiconductorsubstrate material ion a glass superstrate having an integrated array oftwo photovoltaic cells in electrical series with one another; and

FIG. 12 depicts a thin film semiconductor substrate material on a glasssuperstrate having a photovoltaic cells in accordance with oneembodiment of the invention.

BEST MODE AND OTHER MODES FOR CARRYING OUT THE INVENTION

FIG. 1 depicts a thin film semiconductor substrate material 301 on aglass superstrate 302 having an integrated array of two photovoltaiccells 303 and 304 in electrical series with one another. Photovoltaiccell 303 has grooves 305, 306, and 307, each of these grooves havingwalls doped with a p⁺ -type dopant as shown at 308 for groove 305.Grooves 305, 306, and 307 are filled with metal which is in conductingelectrical contact with the respective p⁺ -type doped walls.Photovoltaic cell 303 also has grooves 310 and 311, each of thesegrooves having walls doped with a n⁺ -type dopant as shown at groove312, being one of the grooves forming double groove 309 which is alsopart of cell 303. Double groove 309 comprises groove 312 and groove 320.Groove 320 has walls doped with p⁺ -type dopant and, as alreadyindicated, groove 312 has walls doped with n⁺ -type dopant. Grooves 310and 311 and double groove 309 are filled with metal which is inconducting electrical contact with their respective n⁺ -type dopedwalls.

Substrate material 301 in cell 303 includes oxide or other insulatingmasking layer 313, p⁺ -type layer 314, intrinsic (which can also ben-type or p-type) layer 315, and n⁺ -type layer 316. Grooves 305, 306,and 307 are electrically linked with grooves 309, 310, and 311 by p⁺-type layer 314, layer 315 (if it is n-type or p-type) and n⁺ -typelayer 316, thereby forming a photovoltaic junction where the dopedlinking substrate material forms a junction with differently dopedsubstrate material of opposite polarity.

Photovoltaic cell 304 has grooves 318 and 319, each of these grooveshaving walls doped with a p⁺ -type dopant as shown at groove 320 fordouble groove 309. Grooves 318 and 319 and double groove 309 are filledwith metal which is in conducting electrical contact with theirrespective p⁺ -type doped walls. Photovoltaic cell 304 also has grooves321, 322, and 323, each of these grooves having walls being doped withan n⁺ type dopant as shown at 324 for groove 321. Grooves 321, 322, and323 are filled with metal which is in conducting electrical contact withtheir respective n⁺ -type doped walls.

Substrate material 301 in cell 304 includes optional oxide or otherinsulating masking layer 325, p⁺ -type layer 326, optional intrinsic(which can also be n-type or p-type) layer 327, and n⁺ -type layer 328.In it simplest form layers 325 and 327 would not be included, whichwould mean substrate material 301 would have 2-layers, namely, p⁺ -typelayer 326, and n⁺ -type layer 328. Grooves 320, 318, and 319 areelectrically linked with grooves 321, 322, and 323 by p⁺ -type layer326, layer 327 (if it is n-type or p-type), and n⁺ -type layer 328,thereby forming a photovoltaic junction where the doped linkingsubstrate material forms a junction with differently doped substratematerial of opposite polarity.

Photovoltaic cells 303 and 304 in substrate material 301 are inelectrical series with one another since the metal in groove 310 is inelectrical contact with the metal in groove 318. Grooves 305, 306, 307,309, 310, 311, 318, 319, 321, 322, and 323 extend near to or are incontact with glass superstrate 302 so that n⁺ -type doped walls ofgrooves 309, 310, 311 in cell 303 are substantially electricallyinsulated from n⁺ -type doped walls of grooves 321, 322, 323 in cell 304and p⁺ -type doped walls of grooves 305, 306, and 307 in cell 303 aresubstantially electrically insulated from p⁺ -type doped walls ofgrooves 320, 318, 319 in cell 304.

The high conductivity of the metal in grooves 305, 306, 307, 309, 310,311, 318, 319, 321, 322, and 323 permits current to be transported overlarger distances than would otherwise be possible, allowing the width ofeach cell region 303 and 304 to be very large (eg 20 cm).

The metals in grooves 305 and 321 are electrically linked to load 329via lines 331 and 332.

A preferred substrate material 301 is silicon.

In use, light 330A (typically sunlight) passes through glass superstrate302 or light 330B passes through insulating layer 325 and light ofappropriate wavelength (and which is not reflected) is absorbed bysubstrate silicon. Current is photogenerated at the light illuminatedp-n junctions in cells 303 and 304 and eventually passes through load329 via lines 331 and 332.

In an alternative arrangement, instead of glass superstrate 302, anintrinsic, n⁻ -type or p⁻ -type single crystal, amorphous, orpolycrystalline semiconductor (intrinsic is preferred) superstrate canbe used in its place and layers 313, 314, 315, 316, 325, 326, 327, and328 can be either deposited on substrate 302 or formed from substrate302 itself. In this instance, unless superstrate 302 is sufficientlythin, cells 303 and 304 are illuminated via surface 301.

Referring to FIG. 2, thin film silicon layers 101 and 102 (p-type), 103,104 and 105 (n-type) are deposited from solution in molten metal byknown techniques onto supporting glass superstrate 107 (other knownappropriate techniques for layer formation may be used). Afterdeposition of these layers from solution in molten metal, oxide or otherinsulating masking layer 106 is either grown or deposited on the surfaceof layer 103. Suitable techniques for growing layer 106 include therapid thermal annealing of the surface region of the grown layer in anoxygen ambient or the physical vapor deposition or the chemical vapordeposition of such a layer. A laser is then used to form grooves 108 and109, through layers 101, 102, 103, 104, 105, and 106 to, or approaching,glass superstrate 107 as shown in FIG. 3. Other techniques such asmechanical scribing or grooving or chemical etching or variouscombinations thereof may be used to form the grooves. Additional n-typematerial is then deposited onto the entire exposed layer including thewalls of grooves 108 and 109 from metal solution. When additional n-typematerial is deposited from metal solution the doped layer may bedeposited in such way that it forms selectively in grooved areas sincegenerally growth is more difficult to nucleate on amorphous oxide orother insulating masking layers. When additional n-type material isdeposited from metal solution or otherwise onto the entire exposedlayer, dopant diffusion is prevented in areas covered by the oxide orother insulating masking layer but not in the remainder of the grooves.After the deposition, growth or diffusion of the n-type material intothe walls of grooves 108 and 109 to form n⁺ -type doped groove walls 112and 113 and the removal of unwanted deposited layers, if required by thedetails of the particular sequence, an oxide or other insulating maskinglayer is grown or deposited onto the walls of grooves 108 and 109 (andonto the remaining surface layer, if appropriate). Grooves 110 and 111are then formed using laser etching, plasma etching, mechanical scribingor chemical etching or various combinations thereof through to, orapproaching, glass superstrate 107. Additional p-type material is thendeposited onto the walls of grooves 110 and 111 in an analogous way tothat of the n-type material as described above to form p⁺ -type dopedgroove walls 114 and 115. The oxide or other insulating masking layer isthen removed from grooves 108 and 109. Metal is then deposited to fillgrooves 108, 109, 110, and 111 as shown at 116 by a technique such aselectroless plating to form adjacent cells 117 and 118. Adjacent cells117 and 118 are interconnected at 119. The p and n regions of grooves110 and 109 respectively are physically located very close to eachother.

In FIG. 3 layers 101, 102, 103, 104, 105, and 106 constitute a thin filmsemiconductor substrate material on a glass superstrate 107 having anintegrated array of two photovoltaic cells 117 and 118 in electricalseries with one another. Photovoltaic cell 118 has groove 111 havingwalls doped with a p⁺ -type dopant as shown at 115. Groove 111 is filledwith metal which is in conducting electrical contact with p⁺ -type dopedwalls 115. Photovoltaic cell 118 also has groove 109 having walls 113doped with a n⁺ -type dopant). Groove 109 is filled with metal which isin conducting electrical contact with n⁺ -type doped walls 113.

Substrate material in cell 118 includes oxide or other insulating layer106, and alternating p-type layers 101 and 102 and n-type layers 103,104, and 105. Grooves 109 and 111 are electrically linked by layers 101,102, 103, 104, and 105, thereby forming a photovoltaic junction wherethe doped linking layers form junctions with differently doped substratematerial of opposite polarity.

Photovoltaic cell 117 has groove 110 having walls 114 doped with a p⁺-type dopant. Groove 110 is filled with metal which is in conductingelectrical contact with p⁺ -type doped walls 114. Photovoltaic cell 117also has groove 108 having walls 112 doped with a n⁺ -type dopant.Groove 108 is filled with metal which is in conducting electricalcontact with n⁺ -type doped walls 112.

Substrate material in cell 117 includes oxide or other insulating layer106, and alternating p-type layers 101 and 102 and n-type layers 103,104, and 105. Grooves 108 and 110 are electrically linked by layers 101,102, 103, 104, and 105, thereby forming a photovoltaic junction wherethe doped linking layers form junctions with differently doped substratematerial of opposite polarity.

Photovoltaic cells 117 and 118 are in electrical series with one anothersince the metal in groove 110 is in electrical contact with the metal ingroove 109 at 119. Grooves 108, 110, 109, and 111 extend near to glasssuperstrate 107 so that n⁺ -type doped walls of groove 108 aresubstantially electrically insulated from n⁺ -type doped walls of groove109 in cell 118 and any other n⁺ -type doped walls of grooves of cell118 or other cells in layers 101, 102, 103, 104, 105, and 106. Also, p⁺-type doped walls of grooves of cell 118 or other cells in layers 101,102, 103, 104, 105, and 106.

The high conductivity of the metal in grooves 108, 110, 109, and 111permits current to be transported over larger distances than wouldotherwise be possible, allowing the distance between grooves 108 and 110for cell 117 and the distance between grooves 109 and 111 for cell 118to be very large (eg 10-20 cm).

Referring to FIG. 4, thin film silicon layers 101 and 102 (p-type), 103,104, and 105 (n-type) are deposited from solution in molten metal orother known techniques onto supporting glass superstrate 407. Afterdeposition of these layers from solution in molten metal or equivalent,oxide or other insulating masking layer 106 is either grown or depositedon the surface of layer 103. Suitable techniques for growing layer 106include spraying, screen printing, the rapid thermal annealing of thesurface region of the grown layer in an oxygen ambient or the physicalvapor deposition or the chemical vapor deposition of such a layer. Alaser is then used to form grooves 408 and 409, through layers 101, 102,103, 104, 105, and 106 to, or approaching, glass superstrate 407. Othertechniques such as mechanical scribing or grooving or chemical etchingor various combinations thereof may be used to form the grooves.Additional n-type material is then deposited onto the entire exposedlayer including the walls of grooves 408 and 409 from metal solution orother appropriate or equivalent technique. When additional n-typematerial is deposited from metal solution the doped layer may bedeposited in such way that it forms selectively in grooved areas sincegenerally growth is more difficult to nucleate on amorphous oxide orother insulating masking layers. When additional n-type material isdeposited from metal solution or otherwise onto the entire exposedlayer, dopant diffusion is prevented in areas covered by the oxide orother insulating masking layer. Diffusion of the n-type material intothe walls of grooves 408 and 409 forms n⁺ -type doped groove walls 412and 413. The deposited layers are then removed if required by thedetails of the particular sequence. An oxide or other insulating maskinglayer is then grown or deposited onto the walls of grooves 408 and 409(and onto the remaining surface layer, if appropriate). Grooves 410 and411 are then formed using laser etching, plasma etching, mechanicalscribing, or chemical etching or various combinations thereof throughto, or approaching, glass superstrate 407. Additional p-type material isthen deposited onto the walls of grooves 410 and 411 in an analogousways to that of the n-type material as described above to form p³⁰ -typedoped groove walls 414 and 415. The oxide or other insulating maskinglayer is then removed from grooves 408 and 409. Metal is then depositedto fill grooves 408, 409, 410, and 411 by a technique such aselectroless plating to form adjacent cells 417 and 418. Adjacent cells417 and 418 are interconnected at 419 where the p and n wall regions 414and 413 meet.

In FIG. 4 layers 101, 102, 103, 104, 105, and 106 constitute a thin filmsemiconductor substrate material on a glass superstrate 407 having anintegrated array of two photovoltaic cells 417 and 418 in electricalseries with one another. Photovoltaic cell 418 has groove 411 havingwalls doped with a p⁺ -type dopant as shown at 415. Groove 411 is filledwith metal which is in conducting electrical contact with p⁺ -type dopedwalls 415. Photovoltaic cell 418 also has groove 409 having walls 413doped with a n⁺ -type dopant. Groove 409 is filled with metal which isin conducting electrical contact with n⁺ -type doped walls 413.

Substrate material in cell 418 includes oxide or other insulating layer106, and alternating p-type layers 101 and 102 and n-type layers 103,104, and 105. Grooves 409 and 411 are electrically linked by layers 101,102, 103, 104, and 105 thereby forming a photovoltaic junction where thedoped linking layers form junctions with differently doped substratematerial of opposite polarity.

Photovoltaic cell 417 has groove 410 having walls 414 doped with a p⁺-type dopant. Groove 410 is filled with metal which is in conductingelectrical contact with p⁺ -type doped walls 414. Photovoltaic cell 417also has groove 408 having walls 412 doped with an n⁺ -type dopant.Groove 408 is filled with metal which is in conducting electricalcontact with n⁺ -type doped walls 412.

Substrate material in cell 417 includes oxide or other insulating layer106, and alternating p-type layers 101 and 102 and n-type layers 103,104, and 105. Grooves 408 and 410 are electrically linked by layers 101,102, 103, 104, and 105 thereby forming a photovoltaic junction where thedoped linking layers form junctions with differently doped substratematerial of opposite polarity.

Photovoltaic cells 417 and 418 are in electrical series with one anothersince the metal in groove 410 is in electrical contact with the metal ingroove 409. Grooves 408, 410, 409, and 411 extend near to glasssuperstrate 407 so that n⁺ -type doped walls of groove 408 aresubstantially electrically insulated from n⁺ -type doped walls of groove409 in ell 418 and any other n⁻³⁰ -type doped walls of grooves of cell418 or other cells in layers 101, 102, 103, 104, 105, and 106 and p⁺-type doped walls 414 of groove 410 are substantially electricallyinsulated from p⁺ -type doped walls of groove of cell 418 or other cellsin layers 101, 102, 103, 104, 105, and 106.

The high conductivity of the metal in grooves 408, 410, 409, and 411permits current to be transported over larger distances than wouldotherwise be possible, allowing the distance between grooves 411 and 409in cell 418 and the distance between grooves 410 and 408 in cell 417 tobe very large (eg 20 cm).

The W-shaped double grooves depicted in FIGS. 1 and 4 are produced by acombination of scribing and chemical etching whereas the U shapedgrooves of FIG. 3 are produced by scribing alone or by scribing andetching wherein the etching is only slight and sufficient only forpurposes of cleaning or when the crystallographic orientation is such asto produce the U shape after substantial amounts of appropriate etching.Crystallographic orientation may be selected to give almost any grooveshape in conjunction with appropriate scribing and chemical etching.

Referring to FIG. 5, thin film silicon layers 201 (p⁺ -type), 202 (i orn-type) and 203 (n⁺ -type) are deposited from solution in molten metalor other known techniques onto a supporting glass superstrate 204. As analternative to layers 201, 202, and 203 of the polarities shown in FIG.5, layers 201, 202, and 203 of FIG. 5 can be of opposite polarities tothose depicted. After deposition of these layers from solution in moltenmetal, oxide or other insulating layer 205 is either grown or depositedon the surface of layer 201. Suitable techniques for growing layer 205include the rapid thermal annealing of the surface region of the grownlayer in an oxygen ambient or the physical vapor deposition or thechemical vapor deposition of such layer. A laser is then used to formgrooves 206, 208, 210, 212, 219, 220, 223, and 224 through layers 201,202, 203, and 205 to, or approaching, glass superstrate 204 as shown inFIG. 6. Other techniques such as plasma etching, mechanical scribing, orgrooving or chemical etching or various combinations thereof may be usedto form the grooves, Additional n-type material is then deposited ontothe entire exposed layer including the walls of grooves 206, 208, 210,212, 219, 220, 223, and 224 from metal solution or from doped layersotherwise deposited thereon. When additional n-type material isdeposited from metal solution the doped layer may be deposited in suchway that it forms selectively in grooved areas since generally growth ismore difficult to nucleate ion amorphous oxide or other insulatingmasking layers. When additional n-type material is deposited from metalsolution or otherwise onto the entire exposed layer, dopant diffusion isprevented in areas covered by the oxide or other insulating maskinglayer. Diffusion of the n-type material into the walls of grooves 206,208, 210, 212, 219, 220, 223, and 224 forms n⁺ -type doped groove walls.After removal of deposited layers, if required by the details of theparticular sequence, an oxide or other insulating layer or masking layeris grown or deposited onto the walls of grooves 206, 208, 210, 212, 219,220, 223, and 224 (and onto the remaining surface layer, ofappropriate). Grooves 207, 209, 211, 217, 218, 213, 221, and 222 arethen formed using laser etching, plasma etching, mechanical scribing, orchemical etching or various combination thereof through to, orapproaching, glass superstrate 204. Additional p-type material is thendeposited onto the walls of grooves 207, 209, 211, 217, 218, 213, 221,and 222 in an analogous way to that of the n-type material as describedabove to form p⁺ -type doped groove walls. Grooves 210 and 211 togetherform W-shaped double groove 215 and grooves 212 and 213 together formW-shaped double groove 214. By appropriate geometrical layout as shownin FIG. 6, the n⁺ -type regions and p⁺ -type regions can either act assites for defining the boundaries of individual cells (grooves 210 and212 for n⁺ -type and grooves 211 and 213 for p⁺ -type) or merely ascontact regions for such cells (grooves 206, 208, 219, 220, 223, and 224for n⁺ -type and grooves 207, 209, 217, 218, 221, and 222 for p⁺ -type).The masking layer is then removed from grooves 206, 208, 210, 212, 219,220, 223, and 224. Metal is then deposited to fill or partially fillgrooves 206, 208, 210, 212, 219, 220, 223, 224, 207, 209, 211, 217, 218,213, 221, and 222 by a technique such as electroless plating. The highconductivity of such deposited metal allows current to be transportedover larger distances than would otherwise be possible, allowing thewidth of each cell region 216 to be very large (eg 20 cm) as shown inFIG. 6. Adjacent cells are interconnected where metal in adjacentgrooves (eg grooves 210 and 211) meets.

It will be apparent from FIG. 6 that multiple photovoltaic cells inseries can be constructed on a single superstrate or substrate. In thisregard, for example, reference is made to FIG. 7 which depicts a planview of a system 700 for the production of electricity comprising a thinfilm semiconductor substrate material 705 on a glass superstrate (notshown) having an integrated array of three photovoltaic cells 701, 702,and 703 in electrical series with one another. In system 700, load 704is in electrical communication with conducting material 707 of a firstconductivity type groove of cell 701 via line 706 and a secondconducting material 708 of a second conductivity type groove of cell 703via line 709 except via lines 706 and 709 and load 704. The areas 707,708, 710 and 711 in system 700 depict conducting material in grooves ofthe types shown in FIG. 6 and are not drawn to scale. In system 700,conducting material 707 is not electrically coupled via interconnectingconducting material with conducting material of a second conductivitytype groove of cell 702 or 703. In addition, in system 700 conductingmaterial 708 is not electrically coupled via interconnecting conductingmaterial with conducting material of a first conductivity type groove ofcell 702 or 701 except via lines 706 and 709 and load 704.

As another example that multiple photovoltaic cells in series can beconstructed on a single superstrate or substrate, reference is made toFIG. 8 which depicts a plan view of a system 800 for the production ofelectricity comprising a thin film semiconductor substrate material 806on a glass superstrate (not shown) having an integrated array of fivephotovoltaic cells 801, 802, 803, 804, and 805 in electrical series withone another. In system 800, load 809 is in electrical communication withconducting material 807 of a first conductivity type groove of cell 801via line 808 and a second conducting material 811 of a secondconductivity type groove of cell 805 via line 810. The areas 807, 812,813, 814, 815, and 811 in system 800 depict conducting material ingrooves of the types shown in FIG. 6 and are not drawn to scale. Insystem 800, conducting material 807 is not electrically coupled viainterconnecting conducting material with conducting material of a secondtype groove of cell 802, 803, 804, or 805 except via lines 808 and 810and load 809. In addition, in system 800 conducting material 811 is notelectrically coupled via interconnecting conducting material withconducting material of a first conductivity type groove of cell 804,803, 802, or 801 except via lines 808 and 810 and load 809.

As a further example that multiple photovoltaic cells in series can beconstructed on a single superstrate or substrate, reference is made toFIG. 9 which depicts a plan view of a system 900 for the production ofelectricity, comprising a thin film semiconductor substrate material 906on a glass superstrate (not shown) having an integrated array of fourphotovoltaic cells 901, 902, 903, and 904 in electrical series with oneanother. In system 900, load 909 is in electrical communication withconducting material 907 of a first conductivity type groove of cell 901via line 908 and a second conducting material 911 of a secondconductivity type groove of cell 904 via line 910. The areas 907, 912,913, 914, and 911 in system 900 depict conducting material in grooves ofthe types shown in FIG. 4 and are not drawn to scale. In system 900,conducting material 907 is not electrically coupled via interconnectingconducting material with conducting material of a second conductivitytype groove of cell 902, 903, or 904 except via lines 908 and 910 andload 909. In addition, in system 900 conducting material 911 is notelectrically coupled via interconnecting conducting material withconducting material of a first conductivity type groove of cell 903,902, or 901 except via lines 908 and 910 and load 909.

As yet a further example that multiple photovoltaic cells in series canbe constructed on a single superstrate or substrate, reference is madeto FIG. 10 which depicts a plan view of a system 1000 for the productionof electricity comprising a thin film semiconductor substrate material1006 on a glass superstrate (not shown) having an integrated array offour photovoltaic cells 1001, 1002, 1003, and 1004 in electrical serieswith one another. In system 1000, load 1009 is in electricalcommunication with conducting material 1007 of a first conductivity typegroove of cell 1001 via line 1008 and a second conducting material 1011of a second conductivity type groove of cell 1004 via line 1010. Theareas 1007, 1013, 1014, 1015 and 1011 in system 1000 depict conductingmaterial in grooves of the types shown in FIG. 3 and are not drawn toscale. In system 1000, conducting material 1007 is not electricallycoupled via interconnecting conducting material with conducting materialof a second conductivity type groove of cell 1002, 1003, or 1004 exceptvia lines 1008 and 1010 and load 1009. In addition, in system 1000conducting material 1011 is not electrically coupled via interconnectingconducting material with conducting material of a first conductivitytype groove of cell 1003, 1002, or 1001 except via lines 1008 and 1010and load 1009.

One of the advantages of the approach of FIGS. 3 or 4 is that the thinfilm semiconductor substrate material may simply have one n-type layerand one p-type layer electrically interlinking the p⁺ -type and n⁺ -typegrooves in each cell or may have a plurality of n-type layers and p-typelayers which alternate with one another as shown in FIGS. 3 and 4, forexample, electrically interlinking the p⁺ -type and n⁺ -type grooves ineach cell. For instance, there may be 20 or more n-type layers and 20 ormore p-type layers which alternate with one another as shown in FIGS. 3and 4, for example, electrically interlinking the p⁺ -type and n⁺ -typegrooves in each cell. It is appropriate in view of the relativesimplicity of a photovoltaic cell having one n-type layer and one p-typelayer electrically interlinking the p⁺ -type and n⁺ -type grooves ineach cell to describe such a cell in more detail with reference to FIG.11. In FIG. 11 layers 1101, 1102, and 1103 constitute a thin filmsemiconductor substrate material on a glass superstrate 1107 having anintegrated array of two photovoltaic cells 1117 and 1118 in electricalseries with one another. Photovoltaic cell 1118 has groove 1111 havingwalls doped with a p⁺ -type dopant as shown at 1115. Groove 1111 isfilled with metal which is in conducting electrical contact with p⁺-type doped walls 1115. Photovoltaic cell 1118 also have groove 1109having walls 1113 doped with a n⁺ -type dopant). Groove 1109 is filledwith metal which is in conducting electrical contact with n⁺ -type dopedwalls 1113.

Substrate material in cell 1118 includes oxide or other insulating layer1101, n-type layer 1102, and p-type layer 1103. Grooves 1109 and 1111are electrically linked by layers 1102 and 1103, thereby forming aphotovoltaic junction where the doped linking layers form junctions withdifferently doped substrate material of opposite polarity.

Photovoltaic cell 1117 has groove 1110 having walls 1114 doped with a p⁺-type dopant. Groove 1110 is filled with metal which is in conductingelectrical contact with p⁺ -type doped walls 1114. Photovoltaic cell1117 also has groove 1108 having walls 1112 doped with a n⁺ -typedopant. Groove 1108 is filled with metal which is in conductingelectrical contact with n⁺ -type doped walls 1112.

Substrate material in cell 1117 includes oxide or other insulating layer1101, n-type layer 1102, and p-type layer 1103. Grooves 1108 and 1110are electrically linked by layers 1102 and 1103, thereby forming aphotovoltaic junction where the doped linking layers form junctions withdifferently doped substrate material of opposite polarity.

Photovoltaic cells 1117 and 1118 are in electrical series with oneanother since the metal 1116A in groove 1110 is in electrical contactwith the metal 1116B in groove 1109 via metal bridge 1119. Grooves 1108,1110, 1109, and 1111 extend near to glass superstrate 1107 so that n⁺-type doped walls of groove 1108 are substantially electricallyinsulated from n⁺ -type doped walls of groove 1109 in cell 1118 and anyother n⁺ -type doped walls of grooves of cell 1118 or other cells inlayers 1101, 1102, and 103. Also p⁺ -type doped walls 1114 of groove1110 are substantially electrically insulated from p⁺ -type doped walls115 of groove 1111 in cell 1118 and any other p⁺ -type doped walls ofgrooves of cell 1118 or other cells in layers 1101, 1102, and 1103.

The high conductivity of the metal in grooves 1108, 1110, 1109, and 1111permits current to be transported over larger distances than wouldotherwise be possible, allowing the distance between grooves 1108 and1110 for cell 1117 and the distance between grooves 1109 and 1111 forcell 1118 to be very large (eg 10-20 cm).

FIG. 12 depicts a thin film semiconductor substrate material 1301 on aglass superstrate 1302 having thereon photovoltaic cell 1303.Photovoltaic cell 1303 has grooves 1305, 1306, and 1307, each of thesegrooves having walls doped with a p⁺ -type dopant as shown at 1308 forgroove 1305. Grooves 1305, 1306, and 1307 are filled with metal which isin conducting electrical contact with their respective p⁺ -type dopedwalls. Photovoltaic cell 1303 also has grooves 1310 and 1311 each ofthese grooves having walls doped with a n⁺ -type dopant as shown forgroove 1321 and 1324. Grooves 1310, 1311 and 1321 are filled with metalwhich is in conducting electrical contact with their respective n⁺ -typedoped walls.

Substrate material 1301 in cell 1303 includes oxide or other insulatingmasking layer 1313, p⁺ -type layer 1314, intrinsic (which can also ben-type or p-type) layer 1315 and n⁺ -type layer 1316. Grooves 1305, 1306and 1307 are electrically linked with grooves 1310, 1311, and 1321 by p⁺-type layer 1314, layer 1315 (if it is n-type or p-type) and n⁺ -typelayer 1316 thereby forming a photovoltaic junction where the dopedlinking substrate material forms a junction with differently dopedsubstrate material of opposite polarity. In its simplest form, layers1314 and 1314 would not be included which would mean substrate material1301 would have 2 -layers, namely, p⁺ -type layer 1314, and n⁺ -typelayer 1316. The high conductivity of the metal in grooves 1305, 1306,1307, 1310, 1311, and 1321 permits current to be transported over largerdistances than would otherwise be possible, allowing the width of cellregion 1303 to be very large (eg 20 cm).

The metal in grooves 1305 and 1321 are electrically linked to load 1329via lines 1331 and 1332.

A preferred substrate material 1301 is silicon.

In use, light 1330A (typically sunlight) passes through glasssuperstrate 1302 or light 1330B passes through insulating layer 1313 andlight of appropriate wavelength (and which is not reflected) is absorbedby substrate silicon. Current is photogenerated at the light illuminatedp-n junctions in cell 1303 and eventually passes through load 1329 vialines 1331 and 1332.

In an alternative arrangement, instead of glass superstrate 1302, anintrinsic, n⁻ -type or p⁻ -type single crystal, amorphous, orpolycrystalline semiconductor (intrinsic is preferred) superstrate canbe used in its place and layers 1313, 1314, 1315, and 316 can be eitherdeposited on substrate 1302 or formed from substrate 1302 itself. Inthis instance, unless superstrate 1302 is sufficiently thin, the cell1303 is to be illuminated via surface 1301.

It will be readily apparent to a person skilled in the art from thesystems depicted in FIGS. 1, 3, 4, 6, 7, 8, 9, 10, and 11 that systemswith a large number of photovoltaic cells in electrical series with oneanother can be constructed in an analogous manner to those depicted.

It will be recognized by persons skilled in the art that numerousvariations and modifications may be made to the invention as describedwithout departing from the spirit or scope of the invention as broadlydescribed. For example, the techniques described are not only applicableto silicon and amorphous silicon substrates, but are applicable to anysemiconducting substrate which may be used in a photovoltaic device.

Deposited layers and substrates may not be substantially flat as shownbut may include texture or patterns to reduce reflection from cellsurfaces and also trap light into the cell.

We claim:
 1. A solar cell having:a plurality of alternate p-type andn-type doped semiconductor material layers defining one or moresemiconductor junctions; and two contact structures formed in aplurality of grooves having semiconductor surfaces and extending tocontact the plurality of doped layers, the semiconductor surfaces of thegroove of a first of the contact structures being doped with an n-typedopant, with the semiconductor surfaces of the groove of the second ofthe contact structures being doped with a p-type dopant and each groovecontaining a conducting material in conducting electrical contact withthe respective doped surfaces of the groove, the first contact structureproviding an electrical connection with the n-type doped layers and thesecond contact structure providing an electrical connection with thep-type doped layers.
 2. The solar cell as claimed in claim 1, wherein atleast two p-type layers are separated by an n-type layer.
 3. The solarcell as claimed in claim 1, wherein at least two n-type layers areseparated by a p-type layer.
 4. The solar cell as claimed in claim 1,wherein the plurality of doped layers include at least five alternatep-type and n-type semiconductor material layers.
 5. The solar cell asclaimed in claim 1, wherein at least one pair of adjacent p-type andn-type layers are separated by an intrinsic layer or a lightly dopedn-type or p-type layer.
 6. The solar cell as claimed in claim 1, whereinthe p-type doped layers are doped as p-type or p⁺ -type layers, andwherein the n-type doped layers are doped as n-type or n⁺ -type layers.7. The solar cell as claimed in claim 1, wherein the semiconductormaterial is a material selected from the group consisting of a thin filmmaterial, single crystal material, and polycrystalline material.
 8. Thesolar cell as claimed in claim 7, wherein the material is in the form ofa thin film on a support substrate or a support superstrate.
 9. Thesolar cell as claimed in claim 8, wherein the support substrate orsupport superstrate is glass, quartz, or perspex.
 10. The solar cell asclaimed in claim 1, wherein the semiconductor material is a materialselected from the group consisting of silicon, germanium, CdTe, CuInSe2,GaAs, AlGaAs, GaP, GaAsP, SiC, and InP.
 11. An array of series connectedsolar cells, the array including m solar cells as defined in claim 1,the semiconductor material of each cell being effectively isolated fromthe semiconductor material of the remaining cells other than by way ofdirect interconnection of their respective contact structures, the firstcontact structure of the jth cell being connected to the second contactstructure of the (j-1)th cell in the array, where 1<j≦m.
 12. The arrayof claim 11, wherein the grooves of the first and second contactstructures of each cell are in a pattern of parallel fingers joined byan interconnecting bus, the fingers of the first contact structure beinginterengaged with the fingers of the second structure.
 13. The array ofclaim 12, herein the bus of the first contact structure of the jth cellis in close proximity, substantially parallel, and connected to the busof the second contact structure of the (j-1)th cell of the array toachieve series connection of adjacent cells.
 14. The array of claim 13,wherein the conducting material of connected busses of adjacent cells isintegrated into a single bus conductor.
 15. The array as claimed inclaim 11, wherein the number m of cells is from 2 to 5000 cells.
 16. Thearray as claimed in claim 11, wherein the number n of cells is from 6 to50 cells.
 17. An array of series connected solar cells, the arrayincluding m solar cells, each cell having a plurality of alternatep-type and n-type doped semiconductor material layers defining regionsof alternating dopant type providing one or more semiconductorjunctions, and two contact structures formed in grooves havingsemiconductor surfaces and extending to contact each of the dopedlayers, semiconductor surfaces of the groove of a first of the contactstructures being doped with an n-type dopant, semiconductor surfaces ofthe groove of the second of the contact structures being doped with ap-type dopant and each groove containing a conducting material inconducting electrical contact with the respective doped surfaces of thegroove, the first contact structure providing an electrical connectionwith the n-type doped layers and the second contact structure providingan electrical connection with the p-type doped layers,the semiconductormaterial of each cell being effectively isolated from the semiconductormaterial of the remaining cells other than by way of directinterconnection of their respective contact structures, and the firstcontact of the ith cell being connected to the second contact structureof the (i-1)th cell in the array, where 1<i<m.
 18. The array of claim17, wherein the grooves of the first and second contact structures ofeach cell are in a pattern of parallel fingers joined by aninterconnecting bus, the fingers of the first contact structure beinginterdigitated fingers of the second structure.
 19. The array as claimedin claim 18 wherein the bus of the first contact structure of the ithcell is in close proximity, and connected to the bus of the secondcontact structure of the (j-1)th cell of the array to achieve seriesconnection of adjacent cells.
 20. The array of claim 19, wherein theconducting material of connected busses of adjacent cells is integratedinto a single bus conductor.
 21. The array as claimed in claim 17,wherein the number m of cells is from 2 to 5000 cells.
 22. The array asclaimed in claim 17, wherein the number n of cells is from 6 to 50cells.
 23. The array as claimed in claim 17, wherein each of the mphotovoltaic cells is a p-n photovoltaic solar cell.
 24. The array asclaimed in claim 17, wherein each of the m photovoltaic cells is a n-pphotovoltaic solar cell.
 25. The array as claimed in claim 17, whereinat least two p-type layers of each cell are separated by an n-typelayer.
 26. The array as claimed in claim 17, wherein at least two n-typelayers of each cell are separated by a p-type layer.
 27. The array asclaimed in claim 17, wherein the plurality of doped layers of each cellinclude at least five alternate p-type and n-type semiconductor materiallayers.
 28. The array as claimed in claim 17, wherein at least one pairof adjacent p-type and n-type layers of each cell are separated by anintrinsic layer or a lightly doped n-type or p-type layer.
 29. The arrayas claimed in claim 17, wherein the p-type doped layers of each cell aredoped as p-type or p⁺ -type layers, and wherein the n-type doped layersof each cell are doped as n-type or n⁺ -type layers.
 30. The array asclaimed in claim 17, wherein the semiconductor material of each cell isa material selected from the group consisting of a thin film material,single crystal material, and polycrystalline material.
 31. The array asclaimed in claim 30, wherein the semiconductor material of each cell isin the form of a thin film on a support substrate or a supportsuperstrate.
 32. The array as claimed in claim 31, wherein the supportsubstrate or support superstrate is glass, quartz, or perspex.
 33. Asystem for the production of electricity, the system including:(a) asolar cell cell having:(i) a plurality of alternate p-type and n-typedoped semiconductor material layers defining at least one semiconductorjunction; and (ii) two contact structures formed in groove extending tocontact the plurality of doped layers, semiconductor surfaces of thegroove of a first of the contact structures being doped with an n-typedopant, semiconductor surfaces of the groove of the second of thecontact structures being doped with a p-type dopant and each groovecontaining a conducting material in conducting electrical contact withthe respective doped surfaces of the groove, the first contact structureproviding an electrical connection with the n-type doped layers and thesecond contact structure providing an electrical connection with thep-type doped layers; and (b) an electrical circuit in electricalcommunication with the conducting material of the first contactstructure of the cell, and the conducting material of the second contactstructure of the cell.